Today's Message Index:
----------------------
1. 05:06 AM - Re: 912 UL vibration (Thom Riddle)
2. 06:21 AM - Re: Re: 912 UL vibration (FLYaDIVE)
3. 08:38 AM - 912 i (Jan de Jong)
4. 11:33 AM - Re: Re: 912 UL vibration (U)
5. 01:14 PM - Re: 912 UL vibration (Roger Lee)
6. 03:13 PM - Re: 912 i (Roger Lee)
7. 03:56 PM - Re: Re: 912 UL vibration (FLYaDIVE)
8. 05:59 PM - Re: Re: 912 i (Jan de Jong)
Message 1
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| Subject: | Re: 912 UL vibration |
Roger,
I don't doubt that the spinner on a pusher prop helps airflow past the prop hub
on an installation with a smooth faired engine installation like the Rutan designs
or the BD5. Similar to the tapered trailing edge of a strut fairing being
more important than the tapered leading edge. However, I can't imagine it
doing much good on a pusher with the engine hanging out in the breeze and making
chaotic the surrounding air flow, like on Kolbs and Rans pushers. Sort of like
trying to swat a gnat while being attacked by a swarm of yellow jackets.
Not having done any aerodynamic studies of this, I recognize I could be wrong,
but it doesn't seem plausible to me.
do not archive
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Diamond Katana DA20-A1
Rotax 912 F3
Don't worry about old age... it doesn't last very long.
- Anonymous
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=385283#385283
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| Subject: | Re: 912 UL vibration |
Sacha:
The post about balancing was posted by me, Barry.
There a a couple of ways of doing balancing - Static and Dynamic.
Static only requires a set of edge knives and spindle. This will put you
in the ball park.
Dynamic can be done - With quite difficulty - Using different old fashion
equipment such as the vibratalk or the string & washer. I went with a bit
more modern approach using a photo eye for RPM and an accelerometer to
measure the displacement.
Can it be done by the good builder? Yes. But, not many a builder will
invest an additional $1500 to $2500 for the equipment - Much easier to get
it done for $250 by an A&P.
Barry
On Sat, Oct 13, 2012 at 10:33 PM, Sacha <uuccio@gmail.com> wrote:
>
> Thank you Roger
>
> Is the balancing you refer to a DIY job or does it require specialized
> equipment?
>
> Sacha
>
>
Message 3
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On behalf of my quest for a definitive understanding of the 912 i
electrical system requirements..
Has somebody found a circuit diagram of the central item called Fuse Box
yet?
Thanks,
Jan de Jong
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| Subject: | Re: 912 UL vibration |
Thanks Barry,
No A&Ps where I am, otherwise I'd gladly farm out this kind of stuff, even i
f A&Ps here (I'm in Italy) are no way as cheap as the US :(
The prop seems to be fine now, so I'll just leave it as it is until I find s
omeone who can take a look at it...
On 14/ott/2012, at 15:20, FLYaDIVE <flyadive@gmail.com> wrote:
> Sacha:
>
> The post about balancing was posted by me, Barry.
> There a a couple of ways of doing balancing - Static and Dynamic.
> Static only requires a set of edge knives and spindle. This will put you i
n the ball park.
> Dynamic can be done - With quite difficulty - Using different old fashion e
quipment such as the vibratalk or the string & washer. I went with a bit mo
re modern approach using a photo eye for RPM and an accelerometer to measure
the displacement.
> Can it be done by the good builder? Yes. But, not many a builder will in
vest an additional $1500 to $2500 for the equipment - Much easier to get it d
one for $250 by an A&P.
>
> Barry
>
> On Sat, Oct 13, 2012 at 10:33 PM, Sacha <uuccio@gmail.com> wrote:
>
> Thank you Roger
>
> Is the balancing you refer to a DIY job or does it require specialized equ
ipment?
>
> Sacha
>
> ==========
> -List" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-L
ist
> ==========
> http://forums.matronics.com
> ==========
> le, List Admin.
> ="_blank">http://www.matronics.com/contribution
> ==========
>
>
>
>
>
>
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=========
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=========
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=========
>
Message 5
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| Subject: | Re: 912 UL vibration |
Hi Sacha,
Three different types of balancing. One is done at the prop factory where they
make sure each blade weighs as close to the same as possible and makes sure the
hub is also in a balanced state. This is then sold as a set.
You can do two balances. One is the static balance and put very simply is just
like doing an auto wheel. You put it on a spindle or a balancer and look for
the heavy side which usually is on the bottom and then add weight at the 12 o'clock
position to make the prop equal weight all the way around so there is no
heavy side. Some hang it on string.
The last balance is a dynamic balance. I spent $4K for my dynamic prop balancer.
This machine is attached to the plane and you run it up near your cruise rpm
on the ground and add weights where it suggest to get rid of any out of balance
situations.
Solid props like wood or carbon fiber like a Warp are more likely to be out of
balance to a higher degree than the newer lighter hollow carbon fiber composite
props. Wood can also wick up moisture which will throw them out of balance.
If you have mis-matched blades for your prop they need to be checked for weight
and at least a static balance.
Hi Thom,
Your probably right about air flow with a fully exposed engine. I learned this
from an engineer at Sensenich that did his PHD on this very subject.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=385314#385314
Message 6
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Hi Jan,
Unless info you need is in the Installation manual you probably won't see it until
they come out with a Heavy manit. manual. The lack of the Heavy manual is
one reason you don't see any classes on the injected engine yet. They are still
pulling all the last details together.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=385323#385323
Message 7
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| Subject: | Re: 912 UL vibration |
Scaha:
If you want to do about a weeks worth of research you can find the needed
components to make up your own dynamic balancer. The cost would be about
$150 US.
The only area that you may have problems with is writing the computer code.
There are four fairly simple cods for a balancer:
1 - Choice of prop 2 blade & 3 blade. Others such as 4 and even 6 blade
are multiples of the 2 & 3 blade.
2 - RPM - This is done by identifying one blade and calling it #1 with a
reflective sticky strip. Then a simple photo eye sends and receives a
signal off the reflective strip. Count the reflections and you have RPM
3 - Accelerometer - Well, here you can go from simple to VERY elaborate
BUT! All the operations are the same. Simple as most balancers are use
ONLY one (1) axis. The 'Y' axis. The out put is a voltage that varies
in amplitude as the vibration increases. And the unit of vibration is IPS
(Inches Per Second) Yes you can use mmPS.
4 - This one becomes a little difficult You have to correlate the RPM
with the #1 blade to a o'clock position so you know WHERE in relation to
the #1 Blade the HEAVY point is. Here is where RPM is converted to SECONDS
and the VOLTAGE output of the accelerometer is given a plot of inches OR mm.
Once you know where the Heavy Vibration Point is you add 180 Deg to that
point to find where you should add weight to balance it out. YES - you
could also remove weight fro the heavy point BUT very few people do that.
AND that is probably a good idea.
NEXT PROBLEM: What if you find the heavy point is between blades?
Or, what if there is no place to mount your balance weight? This goes back
to the question I posted where a friend had a Rotax and a three blade prop
and NO place to mount the balance weights.
Well, What you can do is start playing with the indexing of the prop on the
drive shaft. This brings up all sorts on questions and old wives tails -
Since supposedly a compression stroke on the #1 cylinder does not matter
since there is a gear box.
Theory may say one thing while practicality says something else.
The proof is in the pudding.
There a one other way other than a computer program but that has its own
problems ... That would be by using an Oscilloscope and set up
a Lissajous Pattern showing RPM Vs Accelerometer.
Do the simple things first -
Static balance the prop.
Make sure the prop tracks true.
Check you mounts - vibration dampeners - airframe and all components
mounted on the engine as well as any cowlings.
Barry
On Sun, Oct 14, 2012 at 2:32 PM, U <uuccio@gmail.com> wrote:
> Thanks Barry,
>
> No A&Ps where I am, otherwise I'd gladly farm out this kind of stuff, even
> if A&Ps here (I'm in Italy) are no way as cheap as the US :(
>
> The prop seems to be fine now, so I'll just leave it as it is until I find
> someone who can take a look at it...
>
>
> On 14/ott/2012, at 15:20, FLYaDIVE <flyadive@gmail.com> wrote:
>
> Sacha:
>
> The post about balancing was posted by me, Barry.
> There a a couple of ways of doing balancing - Static and Dynamic.
> Static only requires a set of edge knives and spindle. This will put you
> in the ball park.
> Dynamic can be done - With quite difficulty - Using different old fashion
> equipment such as the vibratalk or the string & washer. I went with a bit
> more modern approach using a photo eye for RPM and an accelerometer to
> measure the displacement.
> Can it be done by the good builder? Yes. But, not many a builder will
> invest an additional $1500 to $2500 for the equipment - Much easier to get
> it done for $250 by an A&P.
>
> Barry
>
> On Sat, Oct 13, 2012 at 10:33 PM, Sacha <uuccio@gmail.com> wrote:
>
>>
>> Thank you Roger
>>
>> Is the balancing you refer to a DIY job or does it require specialized
>> equipment?
>>
>> Sacha
>>
>> ==========
>> -List" target="_blank">
>> http://www.matronics.com/Navigator?RotaxEngines-List
>> ==========
>> http://forums.matronics.com
>> ==========
>> le, List Admin.
>> ="_blank">http://www.matronics.com/contribution
>> ==========
>>
>>
>>
>>
> *
>
> *
>
> *
>
> *
>
>
Message 8
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Hi Roger,
I hoped that someone would have "hacked" it for me by now. But there
does not seem to be a lot of amateur action on the 912 i. Which makes
sense ofcourse because it is an expensive toy.
The Installation Manual generates as many questions as it answers. Some
of the "what", none of the "why". And it contains errors.
It is not very urgent yet. I will save my list of questions and revisit
later.
Jan
On 10/15/2012 12:12 AM, Roger Lee wrote:
>
> Hi Jan,
>
> Unless info you need is in the Installation manual you probably won't see it
until they come out with a Heavy manit. manual. The lack of the Heavy manual is
one reason you don't see any classes on the injected engine yet. They are still
pulling all the last details together.
>
> --------
> Roger Lee
> Tucson, Az.
> Light Sport Repairman - Maintenance Rated
> Rotax Repair Center - Heavy Maint. Rated
> Home 520-574-1080 TRY HOME FIRST
> Cell 520-349-7056
>
>
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